1. Field of the Invention
The present invention relates to a rewritable optical storage system and more particularly to a defect area management system and method for an optical storage medium.
2. Discussion of Related Art
An optical storage media is generally divided into a read only memory (ROM), a write once read many (WORM) memory into which data can be written one time, and a rewritable memory into which data can be written several times. Rewritable optical storage media, i.e. optical discs, include rewritable compact discs (CD-RW) and rewritable digital versatile discs (DVD-RW, DVD-RAM, DVD+RW).
The operations of writing and playing back data in rewritable optical discs may be repeated. This repeated process alters the ratio of storage layers for writing data into the optical storage medium from the initial ratio. Thus, the optical discs lose its characteristics and generate an error during recoding/playback. This degradation is indicated as a defect area at the time of formatting, recording on or playing back from an optical storage medium.
Also, the rewritable optical disc may have a defect area due to a scratch on its surface, dirt and dust, or failure during manufacture. Therefore, in order to prevent writing into or reading out of the defect area, management of such defect areas is necessary.
FIG. 1 shows a defect management area (DMA) in a lead-in area and a lead-out area of the optical disc to manage a defect area. Particularly, the data area is divided into groups for the defect area management, where each group is further divided into a user area and a spare area. The user area is where data actually written and the spare area is used when a defect occurs in the user area.
Typically, one disc (e.g. DVD-RAM) has four DMAs, two in the lead-in area and two in the lead-out area. Since managing defect area is important, the same data are held in all four DMAs for data protection. Each DMA includes two blocks and consists of 32 sectors, wherein one block consists of 16 sectors. The first block (DDS/PDL block) of each DMA includes a disc definition structure (DDS) and a primary defect list (PDL), and the second block (SDL block) includes a secondary defect list (SDL).
More specifically, the PDL represents a primary defect data storage area, and the SDL represents a secondary defect data storage area. The PDL stores entries of all defective sectors generated during manufacture and identified during formatting such as initialization or re-initialization. Each entry includes a sector number corresponding to a defective sector and an entry type.
On the other hand, the SDL is arranged by blocks and holds entries of either defective areas which may be generated after initialization or defective areas which cannot be entered in the PDL during initialization. Each entry of the SDL includes an area storing the sector number of a first sector of the block having defective sectors, and an area holding the sector number of a first sector of a replacement block. Defective areas in the data area (i.e., defective sectors or defective blocks) are replaced with new sectors or blocks, respectively by skip defective area technique or linear replacement.
The skip defective area technique is utilized when a defective area or sector is recorded in the PDL. As shown in FIG. 2A, if defective sectors m and n, corresponding to sectors in the user area, are recorded in the PDL, such defective sectors are skipped to the next available sector. By replacing the defective sectors by subsequent sectors, data is written to a normal sector. As a result, the user area into which data is written slips and occupies the spare area in the amount equivalent to the skipped defective sectors.
The linear replacement is utilized when a defective area or block is recorded in the SDL. As shown in FIG. 2B, if defective blocks m and n, corresponding to blocks in either the user or spare area, are recorded on the SDL, such defective blocks are replaced by normal blocks in the spare area and the data to be recorded in the defective block are recorded in an assigned spare area. To achieve the replacement, a physical sector number (PSN) assigned to a defective block remains, while a logical sector number (LSN) is moved to the replacement block along with the data to be recorded. Linear replacement is effective for non real-time processing of data.
FIG. 3 is a partial diagram of an optical disc recording/playback (R/P) device relating to the write operation. The optical disc (R/P) device includes an optical pickup to write data into and playback data from the optical disc; a pickup controller transferring or moving the optical pickup; a data processor either processing and transferring the input data to the optical pickup, or receiving and processing the data reproduced through the optical pickup; an interface; and a micro processor (micom) controlling the components.
Also, a host may be connected to the interface of the optical disc R/P device to transfer commands and data to and from each other. Such host can be any kind of personal computer, and would manage the optical disc R/P device. FIG. 4 shows an optical R/P method.
Referring to FIG. 4, if there is data to be written (Step 401), the host sends both the data to be written and a write command to the optical disc R/P device (Step 402). The write command includes a logical block address (LBA) which designates a write position, and a transfer length which indicates the size of the data to be written.
Upon receiving the data, the optical disc R/P device begins to write the data into a corresponding LBA of the optical disc (Step 403). The optical disc R/P device does not write data into defective areas by utilizing the PDL and SDL, which show defective areas of the optical disc. Thus, the write operation is performed by skipping the physical sector recorded in the PDL or replacing the physical block recorded in the SDL with an assigned block in the spare area.
When the optical disc R/P device completes writing the received data, the optical disc R/P device informs the host of the completion by transferring a write completion signal (Step 403). The host then monitors whether the write command was well executed (Step 404). Finally, the optical disc R/P device sends (Step 405) a command execution report to the host, and the host terminates the data write operation on receipt of the report (Step 406).
However, the above conventional technique has several problems. Because both skipping and linear replacement are utilized, when a defective block is found during data write operation, the defective block may be replaced by an assigned block in the spare area. As a result, the optical pickup must be transferred to the spare area and retransferred back to the user area in order to continue writing the data. The time to transfer and retransfer the optical pickup may become a significant problem in a real-time processing.
Therefore, application of the conventional technique described above would not be effective when real-time writing is required, such as for audio-visual (A/V) use, because of its uniform defect area management.